Review of Scientific Instruments最新文献

The gyrotron operates in the harmonic state, which can significantly reduce the required operating magnetic field but complicates the mode competition problem. In some situations, it is also possible for the backward wave of the fundamental wave mode to be excited to suppress the desired harmonic operating mode. Therefore, a detailed analysis of mode competition is necessary for gyrotrons operating in the harmonic state. This paper presents the theoretical research of mode competition and experimental work for the 28 GHz second harmonic gyrotron at the TE02 mode. Possible mode competition problems are analyzed in detail using the linear theory and the multimode time-dependent non-linear theory. The problem of excitation of the backward wave of the fundamental wave mode TE21, which may be present, is received focused investigation. Ultimately, the possible competition modes are successfully suppressed in the non-linear simulation by setting up a suitable startup scenario, and an interaction efficiency of 32.5% is obtained. Based on the theoretical research results, experimental verification is carried out. When the working voltage is 29.8 kV, the beam current is 1.18 A, and we obtain stable single mode operation of the gyrotron, which has an operation frequency of about 27.96 GHz and an interaction efficiency of about 30.1% from the experiment.

Due to the extremely high pressures in the deep sea, traditional rigid actuators typically require protective vessels and pressure-compensation systems, leading to complex structures and increased risk of structural failure. The inherent adaptability of piezoelectric excitation and friction-coupling drive to high-pressure environments suggests that, theoretically, piezoelectric actuators can operate in full-ocean-depth pressure conditions with an open, direct-immersion structure without requiring bulky pressure-compensation systems. However, the feasibility of piezoelectric actuators operating in full-ocean-depth pressure environments (0-110 MPa) remains unvalidated. To address this, we designed an M-shaped hybrid-mode piezoelectric actuator to experimentally verify its performance under full-ocean-depth pressure conditions. The actuator's structural dimensions were determined using the finite element method to meet the requirements of frequency degeneracy. We developed a high-pressure water simulation system and measured velocity to evaluate the actuator's performance in simulated full-ocean-depth pressure environments. Our results demonstrate that the actuator prototype operates successfully under pressures up to 110 MPa, equivalent to a depth of 11 000 m, the Earth's deepest point. In addition, the actuator's velocity remains stable across hydrostatic pressures ranging from 0 to 110 MPa. Although our experiments focus on the M-shaped hybrid-mode design, this actuator embodies the core principles of piezoelectric excitation and friction-coupling drive, which are broadly applicable to various piezoelectric actuators. By validating this design, we broaden both the structural configurations and driving mechanisms available for piezoelectric actuators and provide key insights into the feasibility of piezoelectric actuators operating under full-ocean-depth pressure conditions.

This paper presents the development of a 1.2 MV high-voltage direct current (DC) power supply with an SF6 insulation for an electrostatic tandem proton accelerator utilized in an accelerator-based boron neutron capture therapy (BNCT) system. BNCT offers a promising alternative to traditional radiation therapy for the treatment of malignant brain tumors, head and neck cancers, and melanomas. The electrostatic tandem proton accelerator system, designed to produce H- ions and subsequently accelerate them to generate protons, represents a significant advancement in medical technology. Key milestones in the process include generating and maintaining a high-voltage DC power supply of 1.2 MV/45 mA for over 30 min, with rigorously testing conducted up to 750 kV/45 mA in ambient conditions. The system features an upgraded Cockcroft-Walton rectifier stage and incorporates a realistic load resistance, with final testing conducted in a tank filled with SF6 gas. Performance tests conducted in atmospheric and SF6 gas environments demonstrate the stable operation of the power supply up to 1.2 MV/45 mA, despite challenges such as corona discharge and electrical arcing in atmospheric environments. It demonstrates excellent long-term voltage and current stability, proving its suitability for tandem proton accelerators by reliably supplying 54 W of power to the dummy load. The developed system can enhance the effectiveness of BNCT systems by generating high-current proton beams, leading to improved treatment outcomes.

A solid-state high voltage pulse power supply with three synchronous output voltages is designed and constructed in this paper. The pulse power supply consists of a fractional-turn ratio saturable pulse transformer and three six-stage Marx generators. The FRSPT not only works as step-up pulse transformers but also as magnetic switches of the Marx generators. All magnetic switches are developed based on two communal cores to achieve a perfect multiple-pulse synchronization effect. The experimental results show that the three output voltages have an amplitude of about 168 kV and a rising time of about 102.6 ns with a 2 MΩ dummy load. The pulse power supply can operate stably at frequencies of 1, 5, 10, and 15 Hz with the synchronization jitters less than 1.5 ns.

We report the design, construction, and automation of a flat plate sample loading, alignment, and data acquisition system for x-ray diffraction measurements in reflection geometry implemented at the Stanford Synchrotron Radiation Lightsource. The system is built onto a single platform, enabling facile transferability, and is compartmentalized into sample storage, sample transfer, and sample position/alignment segments. The core feature of this system is a six-axis robotic arm that offers a large range of highly reproducible and programmable movements. The degrees of freedom of the robot arm enable adaptability in which movements can be modified to fit various beamline environments and sample configurations. The samples are housed on 3D printed sample mounts, which are arranged onto a 6 × 2 array of sample cassettes capable of holding seven samples. Using sample mounts designed for solid oxide electrolysis button cells (SOECs), the maximum tray capacity is 84 samples, which can be aligned and run in ∼24 h with long exposure scans. The sample array is additionally capable of accommodating a range of sample sizes and geometries due to the rapid 3D printed fabrication. The components of the setup will be described in detail and performance will be demonstrated with a set of representative SOEC and XRD standard samples. Opportunities for future developments and integration with the automated setup are summarized.

A bunching system utilizing a heterodyne combiner is designed to generate a sawtooth waveform with three harmonics to increase the beam current intensity of medical cyclotron accelerators. The design incorporates a low-pass filter, helical bandpass filters, and a broadband matching network, producing a sawtooth waveform exceeding 1200 V, which meets the requirements for efficient bunching. This buncher substitutes the design and manufacturing requirements for high linearity broadband power amplifiers with three narrowband single-frequency power amplifiers for amplification. The digital direct synthesizer achieves coherent amplitude and phase adjustment of these three frequency signals. The broadband matching network is based on transmission line transformers to avoid the design of large-sized coaxial resonant cavities, which satisfy the spatial constraints of the cyclotron injection line.

Dynamics of materials under high-pressure conditions has been an important focus of materials science, especially in the timescale of pico- and femto-second electronic and vibrational motion, which is typically probed by ultrafast laser pulses. To probe such dynamics, it requires an integration of high-pressure devices with the ultrafast laser system. The combination of transient absorption (TA) spectroscopy with diamond anvil cells (DACs) is a novel solution, yet the intense pump scattering light resulting from the small cross section of the DAC may limit the spectral range of the detected signal. In this work, we construct a unique frequency-resolved high-pressure TA spectroscopy system based on a double-chopper configuration, which allows for real-time scattering noise collection and effective elimination. This enables us to freely select the pump wavelength based on the sample's dynamics and obtain complete spectral signals. We test a system with a Rhodamine B solution with the probe wavelength range of 450-750 nm and the 550 nm pump and observe that the intensity of the signal peak corresponding to the monomer at 560 nm continuously decreased relative to the signal peak corresponding to the dimer at 530 nm. This indicates that the portion of Rhodamine B molecules in the dimer form increases under increasing pressure. In addition, we find two dynamic components of the signal peaks for both monomer and dimer: the short-lifetime component increases as the pressure is increased, and the long-lifetime component decreases.

Industrial applications of micro-vision tracking algorithms become increasingly prevalent. Unfortunately, out-of-focused-plane (OFP) disturbances negatively impact the in-focused-plane (IFP) tracking accuracy of the micro-vision. This paper proposes a robustness evaluation system for micro-vision tracking algorithms. The relationship between IFP accuracy degradation/improvement and OFP disturbances is quantified. First, a commercial spatial nanopositioning stage (com-SNPS) and an SNPS designed in the laboratory (lab-SNPS) were employed to build a robustness evaluation system. Two SNPSs were utilized to generate both IFP trajectories and specific OFP disturbances. Capacitive sensors were used to evaluate the IFP accuracy of micro-vision tracking algorithms. Second, traditional micro-vision tracking algorithms were selected. The combination of the constant-template matching method, constant-region-of-interest (constant-ROI) retrieval method, and constant-focused-plane focusing method acted as test examples. Third, robust micro-vision tracking algorithms were developed. The variable-template matching method, variable-ROI retrieval method, and variable-focused-plane focusing method were combined. Finally, the prototype of the proposed robustness evaluation system was tested. The focused plane was determined to be a benchmark for calculating OFP disturbances. The IFP accuracy of chosen algorithms under specific OFP excitation was measured. Test results demonstrate different IFP degradation or improvement characteristics of micro-vision algorithms. This paper contributes to developing a robust micro-vision tracking algorithm.

We present a new jet-stirred turbulent water tank designed to produce homogeneous isotropic turbulence, focusing on multiphase flow phenomena. In particular, the facility features a high Taylor-microscale Reynolds number of O(103) that can ensure a large inertial range and is suitable for studying the breakage of droplets and bubbles in line with the Kolmogorov-Hinze theory. The turbulence is created in an octagonal horizontal water tank by two opposing jet arrays, where each jet can release continuous flow with adjustable velocity. The acrylic section design allows optical access for six high-speed cameras to apply time-resolved visualization techniques. Using 3D Lagrangian particle tracking, we provide a complete statistical characterization of the turbulence field: our measurements reveal a maximum turbulence anisotropy of 10% in the center of the water tank with an energy dissipation rate up to ɛ = 0.3 m2 s-3. This high energy dissipation rate is sufficient to trigger the breakage of bubbles and droplets of O(1-10 mm), which falls in the turbulence inertial range. Furthermore, we demonstrate the capability of our imaging system and reconstruction methods for multiphase flow studies with examples of full 3D topology reconstruction coupled with surrounding flow measurements.

Pulsed power technology has found widespread application in environmental governance, biomedicine, food processing, and other fields. This study proposes a pulse generator using forward topology and magnetic superposition to get high-voltage outputs. This design could adjust the pulse width in a relatively larger range by optimizing the coil structure and turns. The isolated power supply and trigger signal are not needed. The RCD (Resistor-Capacitor-Diode) and the third winding are used to reset the remanence. The third winding magnetic reset will take over the resetting process when the capacitor voltage of RCD is over twice the charging voltage if the magnetic flux to be reset is relatively large. By the combination of these two magnetic reset methods, the ringing of the output could be absorbed, the voltage stress on the switch could be limited to about twice the charging voltage, and the efficiency of the system could be improved. The working principle is analyzed and verified by simulation and experiments. Finally, a 20-stage pulse generator is developed, which could generate the pulse with an amplitude of 10 kV and a pulse width of 2-5 µs. With this design, the voltage and current could be easily improved by adding stages and switches in parallel.